Stereoselectivity and kinetics of [4 + 2] cycloaddition reaction of cyclopentadiene to para‐substituted E‐2‐arylnitroethenes

Abstract

In spite of diversified electrophilicity of E‐2‐arylnitroethenes, their [4 + 2] cycloaddition reactions with cyclopentadiene leads to the corresponding 6‐endo‐aryl‐5‐exo‐nitronorbornenes and 6‐exo‐aryl‐5‐endo‐nitronorbornenes as the only reaction products. Stereoselectivity, substituent and solvent effects, and activation parameters, suggest that these reactions occur via a synchronous concerted mechanism on both competing pathways. The experimental results obtained are consistent with the data from B3LYP/6‐31G(d) calculations. Due to high electrophilicity of E‐2‐arylnitroethenes, the reactions studied should be considered as polar [4 + 2] cycloadditions. Copyright © 2011 John Wiley & Sons, Ltd.

An experimental and theoretical study of the hetero Diels–Alder reactions between (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether: one-step or zwitterionic, two-step mechanism?

“…Reports published recently show that the same theoretical level was used e.g. for the exploration of reaction pathways of several DA reactions involving CNA [10,[20][21][22]. In particular, the B3LYP/6-31G(d) calculations illustrate well the structure of transition states (TS) in cycloadditions between cyclopentadiene and CNA.…”

“…For the simulations of dielectric medium presence (methanol e = 32.63; diethyl ether e = 4.34), the PCM algorithm of Tomasi et al [25] was used. The same solvation model was used recently successfully in exploring DA reactions paths between (E)-2-phenylnitroethene and cyclopentadiene [21,26], 3-nitro-1-(p-toluenesulfonyl)-indole and cyclopentadiene [27] as well as in many other similar cases [28][29][30].…”

“…2] cycloaddition mechanism. However, in the case of reactions between strongly electrophilic CNA and p-electron-rich ethylenes as dienophiles, the onestep mechanism may compete with the two-step, zwitterionic mechanism [7]. For example, HDA reactions between (E)-3,3,3-trifluor-1-nitroprop-1-ene and enamines take place via zwitterionic intermediates [8,9].…”

Efficient synthesis of functionalized 1,2,3-triazoles by catalyst-free 1,3-dipolar cycloaddition of nitroalkenes with sodium azide

“…The nitrocoumarines (1a-e), on the other hand, show strongly electrophilic properties (global electrophilicity of (1a) = 3.28, (1b) = 3.55, (1c) = 3.62, (1d) = 3.62, (1e) = 2.94 eV). Their electrophilicity is therefore much higher than of the corresponding β-nitrostyrenes 17 and only slightly lower than of the corresponding β-cyano-β-nitrostyrenes. 18 In the case of a series of β-carboethoxy-β-nitrostyrenes global electrophilicity is significantly lower (in particular: (1i) = 2.64, (1f) = 2.72, (1g) = 2.93, (1h) = 2.93 eV), but remain in the range typical for the strongly electrophilic dipolarophiles.…”

Single crystal X-ray structure of (Z)-1-bromo-1-nitro-2-phenylethene

“…Many β-arylnitroethenes and their derivatives have been documeted to display diverse biological activities including antibacterical 6 , molluscicidal 7,8 and anticancer 9,10,11 . β-arylnitroethenes are also used as versatile intermediates in organic syntheses such as selective reductions to diverse functional groups, the Diels-Alder cycloaddition reactions 12,13 , and the Michael addition 14 .…”